Sound translating device



July 30, 1946. A. F. HORLACHER SOUND 'TIAANSLATING- DEVICE Filed July 9, 1941 IN VENTOR. ALBERT F. HORLACHER WW, M ym ATTORNEYS,

Patented July 30, 1946 SOUND TRAN SLATING DEVICE Albert F. Horlacher, Genoa, 111., assignor to Automatic Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Application July 9, 1941, Serial No. 401,591

8 Claims.

The present invention relates to sound translating devices and more particularly to telephone receivers of the type disclosed in U. S. Patent No. 2,241,105, Woodrufi and Horlacher, granted May 6, 1941.

A telephone receiver of the type mentioned conventionally comprises a casing, a diaphragm mounted on the casing, a transducer unit arranged in the casing and operatively coupled to the diaphragm, and a front assembly secured to the casing and enclosing the diaphragm. The front assembly cooperates with the diaphragm to define a shallow chamber therebetween and has an opening formed therein to provide a restricted passage between the exterior and the chamber.

While a telephone receiver of this character is entirely satisfactory in operation, it does not have the uniformity of response at all frequencies within the frequency range thereof which is desirable.

Accordingly, it is the principal object of the present invention to provide a telephone receiver comprising an improved front assembly which is effective to produce a more uniform response at all frequencies within the frequency range of the receiver.

Another object of the invention is to provide in a telephone receiver, an improved front assembly which is eifective to increase the response in the low frequency band of the range of the receiver.

A further object of the invention is to provide an improved front assembly for a telephone receiver which is of simple and. rugged structure and which is of compact and light-weight construction.

The novel features believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawing, in which Figure 1 is a side elevational view, partly in section, of a telephone receiver embodying a conventional front assembly; Fig. 2 is a plan View of a front assembly for a telephone receiver of the character of that shown in Fig. 1 and embodying the present invention; Fig. 3 is a longitudinal sectional view of the front assembly shown in Fig. 2; Fig. 4 is a modified form of the front assembly and embodying the present invention; and Fig. 5 is a longitudinal sectional View of the front assembly shown in Fig. 4. r

Referring now more particularly to Fig. 1 of the drawing, there is shown a telephone receiver H] of conventional construction and arrangement, which comprises a supporting handle Ii formed of insulating material and provided with a hollow supporting cup [2 adapted to receive a transducer unit l3. Preferably, the transducer unit I3 is. of the construction and arrangement of that disclosed in the previously mentioned Wcodruff and Horlacher patent and comprises a cylindrical cup-shaped casing 14 housing the associated mechanism and an annular dished diaphragm i5 cperatively coupled to the mechanism by an operating rod I6. The enclosing casing 54 is provided with an annular outwardly flared flange l? which is supported upon the annular rim lid of the sup-portin cup l2 and an annular inwardly disposed ledge I8 which supports the peripheral portion of the diaphragm l5.

Also, the receiver I0 comprises a front assembly 19 in the form of an inverted cup-shaped member 28 provided with an annular side wall 2i and a dished bottom wall 22. The rim of the side wall 2| engages the rim l2a of the supporting cup [2 in close surrounding relation with respect to the annular flange I! carried by the casing Id. The interior of the side wall 2i carries two annular shoulders 23 and 2d which respectively engage the annular flange ll carried by the casing I and the peripheral portion of the diaphragm I5. The bottom Wall 22 carries an ear piece 25 formed of insulatin material and provided with a dished bottom wall arranged in nested relation with respect to the bottom wall 22. The front assembly 19 and the ear piece 25 are retained in place upon the supporting cup 12 by a tubular retaining rin 26, the outer end of the retaining ring 26 being flanged over to engage an annular shoulder 27 provided on the ear piece 25 and the inner end of the retaining ring 26 being internally threaded to engage an externally threaded portion I'Zb of the supporting cup 12. Accordingly, the retaining ring 26 clamps the ear piece 25, the front assembly 19 and the annular flange ll provided on the casing Hi securely in place on the annular rim i211 of the supporting cup I2 and clamps the peripheral portion of the diaphragm l5 securely upon the annular ledge l8.

The front assembly is cooperates with the diaphragm l5 to define a shallow chamber 23 therebetween; and the bottom wall 22 has an annular row ofopenings 29 formed therein in order to provide a restricted passage communicating between the exterior and the chamber 28. The

3 annular row of openings 29 formed in the bottom wall 22 is arranged in registry with respect to a centrally disposed circular opening 39 formed in the ear piece 25 in order to prevent interference with the passage of the air between the chamber 28 and the exterior.

During the operation of the receiver it] the input signal to the transducer unit it causes the mechanism housed in the casing I 2 to vibrate the diaphragm l5 through the operating rod l6, whereby the air in the chamber 28 is set into vibration and passes back and forth through the annular row of openings 29 formed in the bottom wall 22, resulting in pressure waves being transmitted to the ear of the user. A conventional telephone receiver of the character described has a response characteristic over an operating frequency range from approximately 400 to 3200 cycles per second, which includes a first peak at approximately 1200 cycles per second corresponding to the fundamental resonance frequency of the diaphragm l5 and a second peak at approximately 2200 cycles per second corresponding to the resonance frequency of the air column in the chamber 28.

In Figs. 2 and 3 of the drawing, there is shown a first form of front assembly 4!] embodying the present invention and comprising an inverted cup-shaped member ll, including an annular side wall 22, and a dished bottom wall 43 constituting an outer plate. Also, the front assembly 49 comprises an inner plate in the form of a dished ring 44 arranged within the member 41, the outer peripheral edge of the inner ring 44 engaging the outer peripheral portion of the bottom wall 43 adjacent the side wall 42 and the inner peripheral edge of the inner ring 44 engaging an annular centrally disposed portion of the bottom wall 43. Preferably, the member 4! and the ring 4 1 are formed of a suitable aluminum alloy and are retained in assembled relation by staking these parts together. The construction of the side wall 42 of the member 4! in the front assembly E is substantially the same as that of the side wall 2| of the member 29 in the front assembly IS in order to clamp the peripheral portion of the associated diaphragm l upon the annular ledge it carried by the casing M of the transducer unit 13. Also a series of annularly spaced-apart threaded holes #55 are provided in the side wall 42 of the member ii in order to accommodate screws, not shown, which are utilized for the purpose of further retaining the associated ear piece in proper angular relation with respect to the member 4!.

A peripheral portion iiia of the outer plate 33 is arranged in spaced relation with respect to the inner ring 44 in order to define a narrow ring-shaped compartment 46 therebetween; while both a central portion 43b of the outer plate 43 and the inner plate M are arranged in spaced relation with respect to the diaphragm 55 in order to define a shallow chamber t? therebetween. A first annular row of openings 48 are formed in the central portion 43b of the outer plate 13 in order to afford a first direct restricted passage between the exterior and the chamber 47; while a second annular row of openings 49 are formed in the outer wall 53 adjacent the central portion 4% thereof and communicating between the exterior and the compartment 43. A third annular row of openings 50 are formed in the inner ring M intermediate the inner and outer peripheral edges thereof and communicating between the compartment 46 and the chamber 47. Accordingly, the openings as and 59 afford a second series sinuous passage through the compartment "55 between the exterior and the chamber ll.

The dimensions of the second restricted passage, including the openings 49, the compartment 36 and the openings 56, are so proportioned and related that this passage has a predetermined mass reactance; while the dimensions of the chamber 4'! are so proportioned and related that this chamber has a predetermined stiffness reactance. More particularly, the mass reactance of the second passage, including the openings =29, the compartment 36 and the openings 56, is so proportioned and related with respect to the stiffness reactance of the chamber 4! that the effective resonance frequency of the diaphragm i5 is substantially reduced with respect to the fundamental resonance frequency thereof. More specifically, it is pointed out that the effective mass reactance of the second passage mentioned increases with frequency, whereby the second passage becomes effectively blocked at a predetermined frequency within the frequency range of the telephone receiver [0. When the effective mass reactance of the second passage mentioned is increased the effective volume of the chamber 4! is decreased due to the blocking of the volume of the compartment 46, whereby the effective stiffness reactance of the chamber 41 is increased. Hence, it will be understood that the effective stiffness reactance of the chamber 41 may be so proportioned and related with respect to the effective mass reactance of the first passage, formed by the openings 48, and the second passage, formed by the openings 49, the compartment is and the openings 56, in parallel, that the chamber ll has first and second resonance frequencies disposed respectively below and above the fundamental resonance frequency of the diaphragm It. By way of example, it is pointed out that the chamber t! may have first and second resonance frequencies disposed approximately at 1000 cycles per second and 2400 cycles per second with respect to the fundamental resonance frequency of 1200 cycles per second of the diaphragm is. This arrangement materially increases the sound output of the telephone receiver in the low frequency band below the fundamental resonance frequency of the diaphragm l5, whereby the response characteristic of the receiver IE] is rendered more nearly uniform over the operating frequency range thereof.

In Figs. 4 and 5 of the drawing, there is shown a modified form of front assembly 63 embodying the present invention and comprising an inverted cup-shaped member GI including an annular side wall 62 and a dished bottom wall 63 constituting an outer plate. Also, the front assembly 60 comprises an inner plate 64 arranged within the member 5!, the outer peripheral edge of the inner plate 84 engaging a shoulder 65 formed on the side wall 62 and the central portion of the inner plate 64 engaging the associated central portion of the outer plate 63. Preferably; the member BI and the inner plate 64 are formed of a suitable aluminum alloy and are retained in assembled relation by an arrangement comprising a rivet 66' extending through centrally located aligned holes provided in the outer plate 63 and the inner plate 64. The construction of the side wall 62 of the member 6| in the front assembly 60 is substantially the same as that of the side wall 2! of the member 20 in the front assembly l9 in order to clamp the peripheral portion of the associated diaphragm l upon the annular ledge I8 carried by the casing [4 of the transducer unit l3. Also, a series of annularly spaced-apart threaded holes 66 are provided in the side wall 62 of the member 6! in order to accommodate screws, not shown, which are utilized for the purpose of further retaining the associated ear piece in proper angular relation with respect to the member 6!.

The principal body portion of the outer plate 63 is arranged in spaced relation with the principal body portion of the inner plate 64 in order to define a narrow ring-shaped compartment 61' therebetween; while the inner plate 64 is arranged in spaced relation with respect to the diaphragm l5 in order to define a shallow chamber 08 therebetween. A first annular row of openings 69 are formed in the central portion of the outer plate 63 and communicating between the exterior and the compartment 51; while a second annular row of openings 10 are formed in the inner plate 64 adjacent the peripheral portion thereof and communicating between the compartment 51 and the chamber 68. Accordingly, the openings 69 and iii afford a series sinuous passage through the compartment 61 between the exterior and the chamber 68.

The dimensions of the restricted passage, in cluding the openings 69, the compartment 61 and the openings 70, are so proportioned and related that this passage has a predetermined mass reactance; while the dimensions of the chamber 68 are so proportioned and related that this chamber has a predetermined stiffness reactance. More particularly, the mass reactance of the passage mentioned is so proportioned and related with respect to the stiffness reactance of the chamber 68 that the effective resonance frequency of the diaphragm I5 is substantially reduced with respect to the fundamental resonance frequency thereof. By way of example, it is pointed out that the effective resonance frequency of the diaphragm it or the predominant resonance frequency of the chamber 68 may be reduced to approximately 1000 cycles per second with respect to the fundamental resonance frequency of 1200 cycles per second of the diaphragm l5. This arrangement materially increases the sound output of the telephone receiver in the low frequency band below the fundamental resonance frequency of the diaphragm [5, whereby the response characteristic of the receiver I0 is rendered more nearly uniform over the operating frequency range thereof.

In a preferred embodiment of the front assembly 60, the compartment 67 has an average thickness of 0.030", an inner diameter of approximately 0.3l3" and an outer diameter of approximately l.602"; six annularly spaced-apart openings 69 are formed in the outer plate 63 and have a diameter approximately 0.0635; and six annular spaced-apart openings '10 are formed in the inner plate 64 and have a diameter approximately 0.0635. Also, in this front assembly 60, the chamber 68 has a diameter of approximately 1.682", a peripheral depth of approximately 0.040" and a central depth of approximately 0.135".

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a sound translating device comprising a cup-shaped casing, an annular diaphragm mounted on said casing and having a fundamental resonance frequency, a transducer unit arranged in said casing and operatively coupled to said diaphragm, and a front assembly secured to said casing and enclosing said diaphragm; said assembly comprising an inverted cup-shaped member having an end wall providing an outer plate, an annular inner plate arranged Within said member, and means including an element extending through aligned centrally disposed holes provided in said plates for securing said plates together, said outer plate being arranged in spaced relation with respect to said inner plate to define a narrow compartment therebetween and having a first annular centrally disposed row of openings therein communicating between the exterior and said compartment, said inner plate being arranged in spaced relation with respect to said diaphragm to define a shallow chamber therebetween and having a second annular peripherally disposed row of openings therein coinmunicating between said compartment and said chamber, said first and second annular rows of openings providing a series sinuous restricted passage through said compartment between the exterior and said chamber, the mass reactance of said passage being so proportioned and related with respect to the stiifness reactance of said chamber that the effective resonance frequency of said diaphragm is substantially altered with respect to the fundamental resonance frequency thereof.

2. In a sound translating device comprising a casing, a diaphragm mounted on said casing, a transducer unit arranged in said casing and operatively coupled to said diaphragm, and a front assembly secured to said casing and enclosing said diaphragm; said assembly having a part spaced from said diaphragm to define a shallow chamber therebetween and comprising a narrow compartment formed therein, a first opening formed therein and providing a direct restricted passage between the exterior of said assembly and said chamber, a second opening formed therein and communicating between the exterior of said assembly and said compartment, and a third opening formed therein and communicating between said compartment and said chamber, said second and third openings providing a series restricted passage through said compartment between the exterior of said assembly and said chamber.

' 3. In a sound translating device comprising a casing, a diaphragm mounted on said casing, a transducer unit arranged in said casing and operatively coupled to said diaphragm, and a front assembly secured to said casing and enclosing said diaphragm; said assembly comprising an outer plate and an inner plate both located on the outer side of said diaphragm, a first portion of said outer plate being arranged in spaced relation with respect to said inner plate to defme a narrow compartment therebetween, a second portion of said outer plate and said inner plate being arranged in spaced relation With respect to said diaphragm to define a shallow chamber therebetween, the second portion of said outer plate having a first opening therein providing a direct restricted passage between the exterior of said assembly and said chamber, the first portion of said outer plate having a second opening therein communicating between the exterior of said assembly and said compartment, said inner 7 plate having a third opening therein communicating between said compartment and said chamber, said second and third openings providing a series restricted passage through said compartment between the exterior of said assembly and said chamber. V

4. In a sound translating device comprising a casing, a diaphragm mounted on said casing, a transducer unit arranged in said casing and operatively coupled to said diaphragm, and a front assembly secured to said casing and enclosing said diaphragm; said assembly comprising an annular outer plate and an inner ring located on the outer side of said diaphragm, the peripheral portion of said outer plate being arranged in spaced relation with respect to said inner ring to define a narrow ring-shaped compartment therebetween, both the central portion of said outer plate and said inner ring being arranged in spaced relation with respect to said diaphragm to define a shallow chamber therebetween, the central portion of said outer plate having a first opening therein providing a direct restricted passage between the exterior of said assembly and said chamber, the peripheral portion of said outer plate having a second opening therein communicating between the exterior of said assembly and said compartment, said inner ring having a third opening therein communicating between said compartment and said chamber, said second and third openings providing a series restricted passage through said compartment between the exterior of said assembly and said chamber.

5. In a sound translating device comprising a casing, a diaphragm mounted on said casing, a transducer unit arranged in said casing and operatively coupled to said diaphragm, and a front assembly secured to said casing on the outer side of said diaphragm; said assembly having a part spaced from said diaphragm to define a shallow chamber therebetween and comprising a narroW compartment formed therein, said assembly being formed to provide a first direct re stricted passage between the exterior of said as sembly and said chamber and a second series re stricted passage through said compartment between the exterior of said assembly and said chamber, the dimensions of said second passage being so proportioned and related that the effective mass reactance thereof increases with fre f quency, whereby said second passage becomes effectively blocked at a predetermined frequency within the frequency range of the device.

In a sound translating device comprising a casing, a diaphragm mounted on said casing and having a fundamental resonance frequency, a transducer unit arranged in said casing and operatively coupled to said diaphragm, and a front assembly secured to said casing on the outer side of said diaphragm; said assembly having a part spaced from said diaphragm to define a shallow chamber therebetween and comprising a narrow compartment formed therein, said assembly being formed to provide a first direct restricted passage between the exterior of said assembly and said chamber and a second series restricted passage through said compartment between the exterior of said assembly and said chamber, the dimensions of said second passage being so proportioned and related that the effective mass reactance thereof increases with frequency in order correspondingly to increase the effective stillness reactance of said chamber, the effective stiffness reactance of said chamber being so proportioned and related with respect to the effective mass reactance of said first and second passages in parallel that said chamber has first and second resonance frequencies disposed re-- spectively below and above the fundamental resonance frequency of said diaphragm.

7. In a sound translating device comprising a casing, a diaphragm, a transducer unit carried by said casing and operatively coupled with said diaphragm, and an assembly unit secured to said transducer unit and comprising a plate spaced from said diaphragm to form a chamber therebetween, said assembly unit also comprising a ring-shaped plate having its inner and outer an nular edges engaging said first-named plate and having its body portion spaced from said firstnamed plate to form an annular compartment, said first-named plate and said ring-shaped plate having openings therethrough which provide a restricted passage from said chamber through said assembly unit.

8. In a sound translating device, a casing, a transducer unit mounted in said casing, a diaphragm located on the outer side of and operatively connected to said transducer unit, and a front assembly unit located on the outer ide of said diaphragm, said assembly unit being in the form of an inverted cup-shaped member having an annular part engaging the edge portion of said diaphragm and a transverse plate spaced from said diaphragm to form a chamber, said assembly unit also having a part spaced from said plate to form a compartment on the outer side of said chamber, said plate and said lastmentioned part having restricted openings therethrough providing passages from said chamber through said compartment to the exterior of said assembly unit, and a perforated ear-piece mount ed on the outer side of said assembly unit.

ALBERT F. HORLACI-IER. 

